This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To use functional and structural MRI to examine brain changes in subjects at risk for HD prior to significant cell loss by scanning at risk HD subjects and controls at two time-points to: 1) evaluate the hypothesis that functional activation of fronto-striatal circuits is abnormal in subjects at risk for HD compared to controls even while subjects are many years away from manifest disease onset. This will be achieved by comparing at risk HD subjects to controls at timepoint 1. 2) evaluate the hypothesis that alterations in frontostriatal function in HD subjects are detectable over a comparatively short interval (approx. 12 months) by scanning each at risk HD subject and control at two time-points.